Polycarbonate articles and adhesive composition therefor

ABSTRACT

An article is disclosed that includes:  
     a) a first polycarbonate substrate;  
     b) a second polycarbonate substrate; and  
     c) an adhesive composition disposed between the first polycarbonate substrate and the second polycarbonate substrate such that the first polycarbonate substrate is bonded to said second polycarbonate substrate through the adhesive composition; the adhesive composition includes an adhesive polymer that includes the reaction product of  
     1) an N-vinyl containing monomer selected from the group consisting of N-vinyl caprolactam, N-vinyl pyrrolidone, and N-vinylimidazole, and combinations thereof, and  
     2) an acrylic acid ester monomer of a non-tertiary alcohol having an alkyl group that includes 4 to 20 carbon atoms.

BACKGROUND OF THE INVENTION

[0001] The invention relates to adhesives for polycarbonate andsurface-coated polycarbonate substrates.

[0002] Digital versatile discs are examples of articles that include twopolycarbonate substrates bonded together through an adhesivecomposition. One or both of the polycarbonate discs may contain data. Toenable the data to be read by an optical reader, at least one of thepolycarbonate discs has a metal-coated surface, e.g., a 50 nm coating ofaluminum. The second polycarbonate disc often has a coating of aluminum,gold, silicon oxide, or silicon carbide.

[0003] One problem in selecting a suitable adhesive composition for thediscs is the potential for polycarbonate to outgas, which makes itdifficult for many adhesives to maintain the integrity of an initiallyformed bond between the adhesive and the surfaces of the discs. Ifdebonding (i.e., adhesive failure and/or cohesive failure) is present,it can be difficult or impossible for the optical reader to read thedata. In addition, many adhesive compositions contain chemical speciesthat corrode the metal coating. The rate of corrosion and debondingtends to increase as humidity and temperature increase.

SUMMARY OF THE INVENTION

[0004] In one aspect, the invention features an article that includes:a) a first polycarbonate substrate, b) a second polycarbonate substrate,and c) an adhesive composition disposed between the first polycarbonatesubstrate and the second polycarbonate substrate such that the firstpolycarbonate substrate is bonded to the second polycarbonate substratethrough the adhesive composition. The adhesive composition includes anadhesive polymer that includes the reaction product of 1) an N-vinylcontaining monomer selected from the group consisting of N-vinylcaprolactam, N-vinyl pyrrolidone, and N-vinylimidazole, and combinationsthereof, and 2) an acrylic acid ester monomer of a non-tertiary alcoholhaving an alkyl group comprising 4 to 20 carbon atoms. In someembodiments, the article is substantially free of debonding after beingsubjected to Accelerated Aging Test Method II.

[0005] In preferred embodiments, the article is substantially free ofdebonding after exposure to 90% relative humidity at 80° C. for 16hours. In other embodiments, the adhesive composition is substantiallyfree of bubbles after the article is exposed to 90% relative humidity at80° C. for 16 hours.

[0006] In one embodiment, the article further includes an inorganiclayer disposed on a surface of the first substrate and the adhesivecomposition is in contact with the inorganic layer. In some embodiments,the inorganic layer is a metal. Example of suitable metals includealuminum, silver, brass, gold, gold alloy, copper, copper-zinc alloy,copper-aluminum alloy, aluminum-molybdenum alloy, aluminum-tantalumalloy, aluminum-cobalt alloy, aluminum-chromium alloy, aluminum-titaniumalloy, and aluminum-platinum alloy and combinations thereof. In someembodiments, the metal layer is reflective to light having a wavelengthfrom 375 nm to 850 mm.

[0007] In another embodiment, the metal layer is substantially free ofcorrosion after the article is subjected to Accelerated Aging TestMethod II. In a preferred embodiment, the metal layer is substantiallyfree of corrosion after the article is exposed to 90% relative humidityat 80° C. for 16 hours, most preferably the metal layer is substantiallyfree of corrosion after the article is exposed to 90% relative humidityat 80° C. for 1000 hours. In other embodiments, the metal layer issubstantially free of corrosion after the article is exposed to 85%relative humidity at 80° C. for 100 hours.

[0008] In some embodiments, the inorganic layer is semi-transparent. Inother embodiments, the inorganic layer is selected from the groupconsisting of gold and Si_(n)X_(m), where X is selected from the groupconsisting of oxygen, nitrogen, carbon, and combinations thereof, andΣ(n+m) satisfies the valence requirements of Si and X.

[0009] In one embodiment, the article further includes a metal layerdisposed on a surface of the first substrate, and an inorganic layerdisposed on a surface of the second polycarbonate substrate, such thatthe adhesive composition is in contact with the metal layer of the firstsubstrate and the inorganic layer of the second substrate.

[0010] In preferred embodiments, the article is optically clear. Inother preferred embodiments, the adhesive composition is opticallyclear.

[0011] In some embodiments, the article is an optical recording medium.The optical recording medium can include data and preferably includes astorage capacity greater than one gigabyte. Examples of suitable opticalrecording media include DVD, DVD-R, DVD-RW, DVD-RAM, DVR, DVD Audio andDVD hybrids.

[0012] In another aspect, the invention features an article thatincludes: a) a first polycarbonate substrate, b) a second polycarbonatesubstrate, and c) an adhesive composition disposed between the firstpolycarbonate substrate and the second polycarbonate substrate such thatthe first polycarbonate substrate is bonded to the second polycarbonatesubstrate through the adhesive composition. The adhesive compositionincludes an adhesive polymer consisting of the reaction product of 1) anN-vinyl containing monomer selected from the group consisting of N-vinylcaprolactam, N-vinyl pyrrolidone, N-vinylimidazole, and combinationsthereof, 2) an acrylic acid ester monomer of a non-tertiary alcoholhaving an alkyl group comprising 4 to 20 carbon atoms, whose homopolymerhas a Tg less than 0° C., 3) optionally a monoethylenically unsaturatedmonomer having from 4 to 20 carbon atoms in the alkyl group, whosehomopolymer has a Tg of greater than 10° C., 4) optionally a substitutedacrylamide, 5) optionally an initiator, 6) optionally a cross-linkingagent, and 7) optionally a chain transfer agent.

[0013] In other aspects, the invention features an adhesive compositionthat includes an adhesive polymer consisting of the reaction productof 1) greater than 30 parts by weight N-vinyl caprolactam (based on 100parts adhesive polymer), 2) an acrylic acid ester monomer of anon-tertiary alcohol having an alkyl group comprising 4 to 20 carbonatoms, whose homopolymer has a Tg less than 0° C., 3) optionally amonoethylenically unsaturated monomer having from 4 to 20 carbon atomsin the alkyl group, whose homopolymer has a Tg of greater than 10° C.,4) optionally a substituted acrylamide, 5) optionally an initiator, 6)optionally a cross-linking agent; and 7) optionally a chain transferagent.

[0014] In one embodiment, the composition is capable of maintaining afirst polycarbonate substrate in fixed relation to a secondpolycarbonate substrate to form an article that is substantially free ofdebonding after the article is subjected to Accelerated Aging TestMethod II.

[0015] In another embodiment, the adhesive composition is capable ofbonding a first polycarbonate substrate to a second polycarbonatesubstrate to form an article that is substantially free of debondingafter exposure to 90% relative humidity at 80° C. for 16 hours.

[0016] In other embodiments, the composition is capable of bonding afirst polycarbonate substrate that includes a metal layer disposed on asurface of the polycarbonate, to a second polycarbonate substrate toform an article that is substantially free of corrosion after exposureto 90% relative humidity at 80° C. for 16 hours.

[0017] In some embodiments, the adhesive composition has a storagemodulus of at least about 2×10⁵ Pa at room temperature.

[0018] In one embodiment, the amount of the N-vinyl caprolactam is fromabout 33 parts by weight to about 50 parts by weight. In otherembodiments, the acrylic acid ester monomer is selected from the groupconsisting of isooctyl acrylate, 2-ethylhexyl acrylate, isononylacrylate, isodecyl acrylate, decyl acrylate, lauryl acrylate, hexylacrylate, butyl acrylate, octadecyl acrylate, and combinations thereof.

[0019] In preferred embodiments, the adhesive composition is opticallyclear. In some embodiments, the adhesive composition is optically clearwhen disposed between a first polycarbonate substrate and a secondpolycarbonate substrate and then exposed to 90% relative humidity at 80°C. for 16 hours.

[0020] In other aspects, the invention features an article that includesa first polyethylene terephthalate substrate comprising siliconedisposed on a surface thereof, a second polyethylene terephthalatesubstrate comprising silicone disposed on a surface thereof, wherein thefirst substrate is different from the second substrate, and a pressuresensitive adhesive composition according to the above-described adhesivecomposition disposed between the first substrate and the secondsubstrate.

[0021] In a further, aspect the invention features an article thatincludes a first polycarbonate substrate, a second polycarbonatesubstrate, and an adhesive composition disposed between the firstpolycarbonate substrate and the second polycarbonate substrate such thatthe first polycarbonate substrate is bonded to the second polycarbonatesubstrate through the adhesive composition, the article beingsubstantially free of debonding after exposure to 85% relative humidityat 80° C. for 100 hours. In a preferred embodiment, the firstpolycarbonate substrate includes data and a metal layer disposed on asurface of the first polycarbonate substrate, and the data is capable ofbeing read according to the DVD Performance Test after exposure to 85%relative humidity at 80° C. for 100 hours.

[0022] In another embodiment, the article includes a first polycarbonatesubstrate, a second polycarbonate substrate, and a pressure sensitiveadhesive composition disposed between the first polycarbonate substrateand the second polycarbonate substrate such that the first polycarbonatesubstrate is bonded to the second polycarbonate substrate through theadhesive composition, and the article is substantially free of debondingafter exposure to 90% relative humidity at 80° C. for 16 hours.

[0023] In other aspects, the invention features an article thatincludes: a) a first polycarbonate substrate, b) a second polycarbonatesubstrate, and c) an adhesive composition disposed between the firstpolycarbonate substrate and the second polycarbonate substrate such thatthe first polycarbonate substrate is bonded to the second polycarbonatesubstrate through the adhesive composition and the adhesive compositionincludes an adhesive polymer consisting of the reaction product of 1) anitrogen containing monomer that is copolymerizable with an acrylic acidester monomer and whose AlogP value is ≦1.0, 2) an acrylic acid estermonomer of a non-tertiary alcohol having an alkyl group comprising 4 to20 carbon atoms, whose homopolymer has a Tg less than 0° C., 3)optionally a monoethylenically unsaturated monomer having from 4 to 20carbon atoms in the alkyl group, whose homopolymer has a Tg of greaterthan 10° C., 4) optionally a substituted acrylamide, 5) optionally aninitiator; 6) optionally a cross-linking agent, and 7) optionally achain transfer agent. In other embodiments, the nitrogen containingmonomer has 0.0≦AlogP ≦1.0. In other embodiments, the acrylic acid estermonomer has an AlogP value greater than 1.0.

[0024] In another aspect, the invention features a method of making theabove-described polycarbonate article. The method includes contactingthe first polycarbonate substrate with the adhesive composition, andcontacting the adhesive composition with the second polycarbonatesubstrate such that the first polycarbonate substrate becomes bonded tothe second polycarbonate substrate through the adhesive composition.

[0025] The invention provides an adhesive composition that is opticallyclear and exhibits excellent bond strength to polycarbonate substratessuch that it maintains the bond under extreme conditions of elevatedrelative humidity (about 90%), and elevated temperature (about 80° C.).The adhesive composition also provides a bond to polycarbonate ofexcellent durability. The bond integrity and the optical clarity arealso maintained when cooled to room temperature after exposure to suchconditions. The adhesive composition is non-corrosive and isparticularly well-suited for use in articles that have corrodiblesurfaces such as articles that include two polycarbonates substrates inwhich one or both of the substrates has a surface coating such asaluminum. The adhesive composition also exhibits good adhesion tosurfaces such as silicon carbide, silicon nitride, and siliconoxide-coated polycarbonate substrates. The adhesive composition can beused in a variety of articles including, e.g., digital versatile discs,e.g., digital video discs, memory switches, vibration dampers, coppercircuitry, and multi-layer polycarbonate articles, e.g., windows, aswell as in general bonding applications.

[0026] Other features of the invention will be apparent from thefollowing description of preferred embodiments thereof, and from theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a cross-sectional view of a polycarbonate article.

[0028]FIG. 2 is a plot of AlogP v. F_(H2O) (Kcal/mol).

DETAILED DESCRIPTION

[0029]FIG. 1 is an example of a polycarbonate article 10 that includes afirst polycarbonate substrate 12 bonded to a second polycarbonatesubstrate 14 through an adhesive composition 18. The polycarbonatearticle may take a variety of forms including that of an opticalrecording medium such as, e.g., a digital versatile disc (DVD), e.g.,DVD, DVD-R, DVD-RW, DVD-RAM, DVD Audio, DVR and DVD hybrids. The formatsfor DVDs have been defined by an industry consortium (ECMA, ExecutiveCommittee of DVD Consortium as ECMA/TC 31/97/2, Geneva Switzerland,January 1997). DVDs can be divided into DVD-ROMs, which are exclusivelyfor reproduction, DVD-RAMs, which can be used for data storage, andDVD-Rs, which are recordable once (write once, read many). The term“DVR” is an acronym for “Digital Video Recordable” disc. Using a lightbeam (light radiation) information can be read out from a DVR and/orinformation can be recorded to a DVR.

[0030] The polycarbonate substrate of the article can be in a variety ofdimensions and shapes including, e.g., a disc, and can include datamolded into the polycarbonate substrate. Useful polycarbonate substratescan also include an inorganic surface layer 16 as shown in FIG. 1. Theinorganic surface layer can include, e.g., metal (e.g., aluminum,silver, brass, gold, a gold alloy, copper, a copper-zinc alloy, acopper-aluminum alloy, an alloy that includes aluminum and a refractorymetal, e.g., molybdenum, tantalum, cobalt, chromium, titanium andplatinum), Si_(n)X_(m), where X is oxygen, nitrogen, or carbon, andΣ(n+m) satisfies the valence requirements of Si and X (e.g., siliconoxide and silicon carbide), and combinations thereof. The inorganicsurface layer may be semi-transparent, i.e., exhibits a reflectivity offrom 18 to 30% as measured according to the ECMA Standard ReflectivityTest Method for 210 mm DVD-ROM. Gold, silicon oxide, and silicon carbideare examples of compounds that are used to form semi-transparent layerson polycarbonate surfaces.

[0031] Examples of commercially available polycarbonate substratesinclude the polycarbonate discs used in digital versatile discs. Thedisc-shaped substrates can have a center hole, which is useful forcentering the DVD's that are assembled therefrom in a recording orplaying station. The disc-shaped substrates can include an outerdiameter of about 50 to about 360 mm, an inner diameter of about 5 to 35mm, and a thickness of between about 0.25 and 1.0 mm.

[0032] The adhesive composition is formulated to maintain adhesion tothe above-described polycarbonate substrates under conditions ofprolonged high humidity and high temperature. In particular, theadhesive composition is capable of maintaining two such polycarbonatesubstrates in fixed relation to each other during and after beingsubjected to Accelerated Aging Test Method II (preferably after exposureto 80° C. and 90% relative humidity for a period of 16 hours, morepreferably after exposure to these conditions after 100 hours, mostpreferably after exposure to these conditions for 1000 hours). Theadhesive composition is also formulated such that the bonded articlemade therefrom is substantially free of debonding after exposure to theafore mentioned conditions. By “substantially free of debonding” it ismeant that, to the extent that adhesive failure at thesubstrate/adhesive interface, cohesive failure of the adhesivecomposition or a combination thereof exists, the bonded article remainscapable of being used for its intended purpose. With respect to adigital versatile disc, for example, to the extent that debonds exist,the disc maintains its data storage and reading functions (i.e., thedisc can be read by an optical reader).

[0033] Preferably the adhesive composition is formulated such that whenemployed in a bonded article such as an optical recording media, e.g., adigital versatile disc, the article can be read, for example, by aDVD200MG Data Analyzer (C. D. Associates Inc., Irvine, Calif.),according to the DVD Performance Test Method set forth in the Examplessection below, after the article has been exposed to 80° C. and 85%relative humidity for a period of 16 hours, more preferably afterexposure to these conditions for 100 hours, most preferably afterexposure to these conditions for 1000 hours.

[0034] The adhesive composition is also preferably noncorrosive suchthat when the composition is adhered to one or more substrates thatinclude a corrodible surface, e.g., metal surface layers, the bondedarticle, after exposure to prolonged conditions of high humidity andhigh temperature, is substantially free of corrosion and debonding.Corrosion can be detected in the bonded article by viewing the articlewith the human eye under normal lighting conditions, including directinga light so that it will pass through the substrate in areas wherecorrosion has occurred. Corrosion is present in areas that appear toexhibit an absence of corrodible layer where the corrodible layer hadpreviously existed on the article. By “substantially free of corrosion”it is meant that to the extent corrosion is present, the article remainscapable of being used for its intended purpose. Preferably the bondedarticle is substantially free of corrosion after exposure to 80° C. and90% relative humidity for a period of 16 hours, more preferably afterexposure to these conditions for 1000 hours.

[0035] The adhesive composition is also preferably optically clear whenviewed by the human eye under normal lighting conditions. Preferably theadhesive composition exhibits at least about 90% transmittance at 650 nmand at a coating thickness of less than about 60 μm, and maintains itsoptical clarity after exposure to the afore mentioned conditions. It ispreferred that the adhesive composition be free of haze, i.e., thewhitening of an originally clear adhesive as observed by the eye understandard lighting conditions, which can impair the optical clarity ofthe adhesive composition, and therefor the ability of an article madetherewith to perform as intended. It is also preferred that the adhesivecomposition be free of bubbles, i.e., gaseous inclusions, which canimpair the optical clarity of the adhesive composition, and the abilityof an article made therewith to perform as intended. The adhesivecomposition can be formulated to exhibit optically clarity afterexposure to extreme humidity and temperature conditions.

[0036] The adhesive composition can also be formulated to impartadditional rigidity to an article bonded therewith, preferablysufficient rigidity to render the article suitable for its intendedpurpose. One measure of the ability of the adhesive composition tomaintain adhesion to a substrate, and to impart sufficient rigidity toan article bonded therewith so as to render the article suitable for itsintended purpose, is its storage modulus (G′). Preferably the adhesivecomposition exhibits a room temperature storage modulus of at leastabout 2×10⁵ Pascal (Pa) when measured according to the Storage ModulusTest Method.

[0037] The adhesive composition includes an adhesive polymer thatincludes the reaction product of N-vinyl containing monomer (preferablyat least about 30 parts by weight, more preferably at least about 33parts by weight, more preferably from about 33 parts by weight to about50 parts by weight), an acrylic acid ester monomer of a non-tertiaryalcohol having an alkyl group of from 4 to 20 carbon atoms and,optionally, a monoethylenically unsaturated modulus reinforcing monomerhaving a homopolymer whose glass transition temperature (Tg) is greaterthan 11° C. (more preferably greater than 25° C.), a substitutedacrylamide, an initiator, a crosslinking agent, a chain transfer agent,and combinations thereof. When bonding two polycarbonate substratestogether, or when adhering a first metallized polycarbonate substrate toa second polycarbonate substrate, the adhesive polymer preferablyconsists of the reaction product of at least about 33 parts by weightN-vinyl containing monomer, the acrylic acid ester monomer, and aphotoinitiator. When adhering a first metallized polycarbonate substrateto a second inorganic surface coated polycarbonate substrate, theadhesive polymer preferably consists of the reaction product of at leastabout 30 parts by weight N-vinyl containing monomer, the acrylic acidester monomer, and a photoinitiator.

[0038] The N-vinyl containing monomer preferably has a AlogP value(i.e., the log of the water-octanol partition coefficient) that is lessthan 1.0, preferably 0.00≦AlogP≦1.0. Preferred N-vinyl containingmonomers include N-vinyl caprolactam, N-vinyl pyrrolidone, andN-vinylimidazole.

[0039] The acrylic acid ester monomer preferably has an AlogP value thatis greater than 1.0. The preferred acrylic acid ester monomer is amonofunctional acrylic acid ester monomer of a non-tertiary alkylalcohol having from 4 to 20 carbon atoms (preferably from 4 to 18 carbonatoms, more preferably 4 to 14 carbon atoms), whose homopolymer has a Tgless than 0° C. (preferably less than about −20° C.). Included in thisclass of acrylic acid ester monomers are 2-methylbutyl acrylate,isooctyl acrylate, 4-methyl-2-pentyl acrylate, isoamyl acrylate,sec-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isononylacrylate, isodecyl acrylate, isodecyl methacrylate, n-decyl acrylate,lauryl acrylate, n-octyl acrylate, n-hexyl acrylate, butyl acrylate,octadecyl acrylate, and combinations thereof.

[0040] The monoethylenically unsaturated monomer having a homopolymer Tggreater than 10° C. (more preferably greater than 25° C.) is preferablysuitable for reinforcing (i.e., increasing) the modulus of the adhesivecomposition. Examples of suitable monoethylenically unsaturated monomershaving a homopolymer Tg of greater than 10° C. include monofunctionalunsaturated monomers. Examples of such monomers include methylacrylate,ethylacrylate, methylmethacrylate, ethyl methacrylate, vinyl acetate,vinyl propionate, 2-(phenoxy)ethyl acrylate or methacrylate, andcombinations thereof. Nonpolar monomers such as isobornyl acrylate mayalso be used.

[0041] Examples of suitable substituted acrylamides include t-butylacrylamide and diacetone acrylamide. Preferably the amount ofsubstituted acrylamide included in the reaction to produce the adhesivepolymer is from 0 to 9 parts by weight based on 100 parts adhesivepolymer.

[0042] The monomer mixture can be polymerized by various conventionalfree radical polymerization methods, whether thermally or radiationinitiated, including, e.g., solvent polymerization, emulsionpolymerization, bulk polymerization and radiation polymerizationincluding processes using ultraviolet light, electron beam radiation,and gamma radiation.

[0043] Solution polymerization involves combining the monomer componentsalong with a suitable inert organic solvent and a free radicallycopolymerizable crosslinking agent in a reaction vessel. After themonomer mixture is charged to the reaction vessel, a concentratedthermal free radical initiator solution is added. The reaction vessel isthen purged with nitrogen to create an inert atmosphere. Once purged,the reaction vessel is sealed, and the solution within the vessel isheated to the activation temperature of the initiator. The mixture isstirred during the course of the polymerization reaction to produce theadhesive composition. Solvent polymerization is well known in the artand described in various sources such as U.S. Pat. No. Re 24,906(Ulrich), and U.S. Pat. No. 4,554,324 (Husman et al.).

[0044] Emulsion polymerization is also described in U.S. Pat. No. Re24,906 in which the monomers are added to distilled water with anemulsifying agent and suitable initiators in a reaction vessel, purgedwith nitrogen, and heated, typically to a temperature in the range ofabout 25° to 80° C., until the reaction is completed.

[0045] The adhesive composition can also be prepared by bulkpolymerization methods in which the adhesive composition, including themonomers and a free radical initiator, is coated onto a flat substratesuch as a polymeric film, and exposed to an energy source in a lowoxygen atmosphere, i.e., less than 1000 parts per million (ppm), andpreferably less than 500 ppm, until the polymerization is substantiallycomplete.

[0046] Alternatively, a sufficiently oxygen free atmosphere can beprovided by enclosing the composition with, for example, a polymericfilm, or enveloping the composition within a packaging material, e.g., apouch. In one embodiment, the film can be overlaid on top of the coatedadhesive composition before polymerization. In another embodiment, theadhesive composition is placed in pouches, which can be optionallysealed, and then exposed to energy, such as heat or ultravioletradiation to form the adhesive.

[0047] The preferred polymerization method includes a two step freeradical polymerization of 100% solids monomer mixture. In the firststep, the low viscosity monomers are mixed at the appropriate ratios andan initiator is added to the mixture. The mixture is purged withnitrogen to remove dissolved oxygen. The composition is partiallypolymerized to produce a syrup with moderate viscosity that can becoated easily. Further initiator and, optionally, a crosslinking agent,an additional monomer, and combinations thereof, are added to the syrup.The syrup is then coated (while excluding oxygen) at a desiredthickness. During or after the coating process the syrup is furtherexposed to energy to complete the polymerization and crosslink theadhesive composition. The free radical polymerization is preferablyperformed by ultraviolet radiation.

[0048] Polymerization methods can also employ thermal radiation. Thecomposition includes a thermal initiator and can be coated onto arelease treated film and covered with a second release treated film. Thecomposite is then placed in a heat transfer fluid and heated to atemperature sufficient to effect polymerization.

[0049] Useful free radical initiators include thermal and photoactiveinitiators. The type of initiator used depends on the polymerizationprocess. Preferably the initiator is a photoinitiator and is capable ofbeing activated by UV radiation, e.g., at wavelengths from about 250 nmto about 450 nm, more preferably at about 351 nm. Useful photoinitiatorsinclude, e.g., benzoin ethers such as benzoin methyl ether and benzoinisopropyl ether, substituted benzoin ethers such as anisoin methylether, substituted acetophenones such as2,2-dimethoxy-2-phenylacetophenone, and substituted alpha-ketols such as2-methyl-2-hydroxypropiophenone. Examples of commercially availablephotoinitiators include Irgacure 819 and Darocur 1173 (both availableform Ciba-Geigy Corp., Hawthorne, N.Y.), Lucern TPO (available fromBASF, Parsippany, N.J.) and Irgacure 651, which is available fromCiba-Geigy corporation and is believed to be2,2-dimethoxy-1,2-diphenylethane-1-one. Also useful are copolymericphotoinitiators.

[0050] Examples of suitable thermal initiators include peroxides such asbenzoyl peroxide, dibenzoyl peroxide, dilauryl peroxide, cyclohexaneperoxide, methyl ethyl ketone peroxide, hydroperoxides, e.g., tert-butylhydroperoxide and cumene hydroperoxide, dicyclohexyl peroxydicarbonate,2,2,-azo-bis(isobutyronitrile), and t-butyl perbenzoate. Examples ofcommercially available thermal initiators include initiators availablefrom DuPont Specialty Chemical (Wilmington, Del.) under the VAZO tradedesignation including VAZO 64 (2,2′-azo-bis(isobutyronitrile)) and VAZO52, and Lucidol 70 from Elf Atochem North America, Philadelphia, Pa.

[0051] The initiator is used in an amount effective to facilitatepolymerization of the monomers and the amount will vary depending upon,e.g., the type of initiator, the molecular weight of the initiator, theintended application of the resulting adhesive composition and thepolymerization process. The initiators can be used in amounts from about0.001 part by weight to about 5 parts by weight based on 100 partsadhesive polymer. Preferred amounts range from about 0.05 part by weightto about 3 parts by weight.

[0052] The adhesive composition may be crosslinked to achieve a desiredstorage modulus, although the adhesive composition preferably exhibitsthe desired storage modulus in the absence of crosslinking. Crosslinkingcan be achieved without a crosslinking agent by using high energyelectromagnetic radiation such as gamma or electron beam radiation. Inaddition, a crosslinking agent, or a combination of crosslinking agentscan be added to the mixture of polymerizable monomers to facilitatecrosslinking and to achieve the desired storage modulus for the adhesivecomposition. The degree of crosslinking in the adhesive composition canbe such that the gel fraction of the adhesive composition is at leastabout 95%.

[0053] Useful cross-linking agents for radiation curing, includemultifunctional acrylates, such as those disclosed in U.S. Pat. No.4,379,201 (Heilmann et al.), which include 1,6-hexanediol diacrylate,trimethylolpropane triacrylate, 1,2-ethylene glycol diacrylate,pentaerythritol tetracrylate, 1,12-dodecanol diacrylate, andcombinations thereof, and co-polymerizable aromatic ketone co-monomerssuch as those disclosed in U.S. Pat. No 4,737,559 (Kellen et al.).Various other crosslinking agents with different molecular weightsbetween (meth)acrylate functionality would also be useful. Suitableultraviolet light sources are, e.g., medium pressure mercury lamps andultraviolet black light.

[0054] Generally, when a crosslinking agent is used, the crosslinkingagent is present in an amount of about 0.01 part to about 0.50 part byweight based on 100 parts adhesive polymer, preferably about 0.05 partby weight to about 0.3 part by weight crosslinking agent.

[0055] Preferred chain transfer agents have a non-corrosive effect onthe metallized surface of a polycarbonate substrate, and are soluble inthe monomer mixture prior to polymerization. Examples of suitable chaintransfer agents include triethyl silane and mercaptans.

[0056] The adhesive composition is preferably in the form of a layer ofcurable liquid or film (e.g., a pressure sensitive adhesive film) at thesurface of the substrate. The thickness of the adhesive coating issufficient to permit polycarbonate substrates to bond to each otherthrough the adhesive composition. The thickness of the adhesive coatingmay vary depending on the application. For digital versatile discs,e.g., the thickness is preferably from about 50 μm to about 75 μm, morepreferably from about 55 μm to about 65 μm.

[0057] The adhesive composition may be coated onto a release-treatedsurface, e.g., a release liner, and then laminated to a surface of apolycarbonate substrate. Alternatively, the adhesive composition may beapplied directly to a surface of the polycarbonate substrate, followedby polymerization of the adhesive composition and, optionally, a releasetreated surface can then be laminated to the adhesive composition. Whenthe adhesive composition is provided in the form of a film, itpreferably is sandwiched between two release liners where one of therelease liners has a release coating that exhibits a lesser degree ofadhesion to the adhesive film relative to the release coating of thesecond release liner. Examples of useful commercially availablepolyethylene terephthalate (PET) backed-silicone release compoundtreated release liners include silicone treated PET release linersavailable under the trade designations P-10 and T-50 from CPFilms,Martinsville, Va.

[0058] In addition to the above-described polycarbonate substrates, avariety of substrates can be bonded to each other through the adhesivecomposition including, e.g., ethylene vinyl acetate, PET, orientedpolypropylene, glass, and combinations thereof. Preferably the adhesivecomposition is formulated to maintain adhesion to two substrates of abonded article where the substrates are ethylene vinyl acetate, PET,oriented polypropylene, glass and combinations thereof, after the bondedarticle has been aged for sixteen hours at 85° C. and 85% relativehumidity.

[0059] The invention will now be described further by way of thefollowing examples. All parts, ratios, percents and amounts stated inthe Examples are by weight unless otherwise specified.

EXAMPLES

[0060] Test Procedures

[0061] Test procedures used in the examples include the following.

[0062] Accelerated Aging Test Method I

[0063] A sample is placed in an oven at 80° C. and 90% relative humidityfor 16 hours. Upon completion of the aging cycle, the sample is visuallyexamined at test temperature and during and upon cooling to roomtemperature for haze, bubbles, pinholes, corrosion, and debonding.

[0064] Bubbles are recorded if there is a gaseous inclusion within themass of adhesive.

[0065] Pinholes are recorded if there are very small areas in thereflective layer that are transmissive to visible light. These are oftenpresent in the virgin reflective layer (i.e., prior to the presence ofthe adhesive composition). It may be necessary to illuminate orbacklight the reflective layer to observe the pinholes.

[0066] Corrosion is recorded if there are areas in the reflective layerthat are transmissive to visible light. The areas of corrosion areinitially larger in size than the pinholes and continue to increase insize, often leading to the complete disappearance of the reflectivelayer of a bonded assembly.

[0067] Debonding occurs if the adhesive composition separates from oneor more of the substrates.

[0068] Accelerated Aging Test Method II

[0069] A sample is placed in an oven at 95% relative humidity where itis subjected to six cycles in which each cycle includes increasing theoven temperature from 25+/−3° C. to 40+/−2° C. and then holding the oventemperature at 40+/−2° C. for a period of 12 hours followed bydecreasing the oven temperature from 40+/−2° C. to 25+/−3° C. and thenholding the oven temperature at 25+/−3° C. over a period of 12 hours.Upon completion of the six cycle aging test, the sample is examined attest temperature and during and upon cooling to room temperature forhaze, bubbles, pinholes, corrosion, and debonding.

[0070] 90° Peel Strength Test Method

[0071] The peel strength of the adhesive composition is measured asfollows. An adhesive film provided on a release liner is prepared byremoving the release liner to expose the adhesive composition. A pieceof 0.05 mm (2 mil) aluminum foil is placed on the exposed adhesivesurface. Using a 102 mm×51 mm (4″×2″) plastic squeegee, the aluminumfoil is adhered to the adhesive by applying hand pressure, whileensuring that no air bubbles or wrinkles are introduced into the testspecimen. The remaining exposed adhesive surface is then adhered to aclean dry piece of test surface (1.3 cm wide). Peel strengthmeasurements are then made using a 90° peel mode at 30.5 cm/min.

[0072] 180° Peel Strength Test Method

[0073] The peel strength of the adhesive composition is measuredaccording to ASTM D3330-90 (Reapproved 1994) Test Method B. Briefly, anadhesive film provided on a release liner is prepared by removing therelease liner to expose the adhesive composition. A piece of 0.05 mm (2mil) aluminum foil is placed on the exposed adhesive surface. Using a102 mm×51 mm (4″×2″) plastic squeegee, the aluminum foil is adhered tothe adhesive by applying hand pressure while ensuring that no airbubbles or wrinkles are introduced into the test specimen. The remainingexposed adhesive surface is then adhered to a clean dry piece of testsurface (1.3 cm wide). Peel strength measurements are then made using a180° peel mode at 30.5 cm/min.

[0074] Cleavage Test Method

[0075] On the unbonded surface of a sample that includes twopolycarbonate DVD substrates bonded together through an adhesivecomposition a circular area of about 2.5 cm in diameter is rubbed with acotton swab treated with toluene. This treatment results in solventattack on the unbonded side of the bonded assembly. A piece of 3M Scotchbrand 851 tape (Minnesota Mining and Manufacturing (3M Company), St.Paul, Minn.) is bonded to the vertical surface of the assembly andadjacent to the solvent treated area, with the tape extending above andbelow the horizontal plane of the bonded assembly. About 2.5 grams ofScotch-Weld DP-420 liquid adhesive (3M Company) is dispensed onto thetape-dammed solvent treated area of the bonded assembly and spread outwith a wooden spatula. A steel tee nut (0.79 cm ({fraction (5/16)}″)) 18international thread, 1.6 cm (⅝″) barrel height) is placed onto theScotch-Weld DP-420 liquid adhesive and positioned such that the edge ofthe steel tee nut is coincident with the edge of the bonded assembly.Additional Scotch-Weld DP-420 liquid adhesive is dispensed so as tofully cover the collared area of the steel tee nut. The assembly isallowed to cure for four hours, after which a second steel tee nutassembly is similarly mounted on the second unbonded horizontal surfaceof the bonded assembly. The cleavage test specimen is then allowed tostand for 16 hours to allow for full cure of the Scotch-Weld DP-420liquid adhesive. A 5.1 cm (2 in.) long threaded bolt is threaded intoeach of the steel tee nuts. The bolts are mounted into the di-opposedjaws of an Instron such that the bonded assembly is subjected to a forcenormal to its bondline. The joint is stressed at a rate of 0.254 cm/minand the force required to initiate separation of the bonded assembly, asmeasured in lbs of force to initiate cleavage, is recorded as thecleavage strength of the bonded assembly.

[0076] Storage Modulus (G′) Test Method

[0077] An adhesive film having a thickness of about 2 mm is prepared bylayering 40 layers of 50 μm thick adhesive film on top of each other andpunching out an 8 mm disc from the adhesive tape. The sample is placedin a Dynamic RDA II rheology analyzer (Rheometric Scientific, Inc.,Piscataway, N.J.) and measurements are made in parallel plate mode at afrequency of 6.28 radians/sec and a strain of 0.5%. The temperature isscanned over a predetermined temperature range at a rate of 5° C./min,with data recordings made every 20 seconds in Pascals (Pa). The storagemodulus (G′) values at −30° C., 23° C. and 80° C. are reported in Pa.

[0078] Optical Clarity Test Method

[0079] Optical clarity is determined using a transmission accessorymounted on a Gardner BYK Color TCS Plus (TM) spectrophotometer (BYKGardner, Columbia, Md.). The spectrophotometer includes software capableof obtaining spectral data at 10 nm intervals from 380 to 720 nm.

[0080] The sample is prepared by cutting a 40 mm×40 mm adhesive samplefrom a 50 μm thick adhesive film sandwiched between a T-50 release linerhaving a 50 μm polyethylene terephthalate (PET)-backing coated with asilicone release compound (CPFilms, Martinsville, Va.), and a P-10release liner having a 50 μm PET backing coated with a silicone releasecompound (CPFilms). One release liner is peeled away exposing theadhesive composition, which is then laid flat onto a 3M Infrared Card(Type 61) (3M Company), which has been modified by enlarging the cardaperture such that the diameter of the aperture is 25 mm on each of itsfour sides. Using a hand held squeegee, pressure is applied to the edgesof the release liner side of the adhesive film to secure the adhesive tothe IR card. The second release liner is then peeled away from theadhesive film and the IR card is mounted on the transmission accessoryunit such that the adhesive-coated side of the IR card is farthest fromthe incident radiation source. The spectral data from 380 nm to 720 nmis then obtained and the % transmission at 650 nm is reported.

[0081] AlogP and F_(H2O)Determination

[0082] AlogP is a parameter that represents the hydrophobic interaction,i.e., the corresponding energy that operates between two or more solutesin water and n-octonal. AlogP=Σn_(i)a_(i), where n_(i) is the number ofatoms of type i in the molecule, and a_(i) is the contribution of thecorresponding atom type.

[0083] F_(H2O) is a parameter that represents the aqueous dissolutionfree energy using a hydration shell model. F_(H2O)=Σn_(i)Δf_(i), wheren_(i) is the number of chemical fragments in a molecule of interest andf_(i) is the aqueous dissolution free energy of the chemical fragment.

[0084] AlogP and F_(H2O) values were calculated for the molecules ofinterest using Cerius2 (Version 3.8) QSAR+ software program (MolecularSimulations Inc.). The molecular structures are optimized with theCOMPASS force field (version 98/01) (Molecular Simulations Inc.).

[0085] AlogP and F_(H2O) values were obtained for each of the followingmonomers and are depicted in the form of the graph of FIG. 2: NVC, NVP,dimethyl acrylamide (DMA), t-butyl methacrylamide (t-BMA), diacetoneacrylamide (DAA) (Aldrich, Milwaukee, Wis.), N-vinylimidazole (NVI),INA, IOA, EHA, and isobornyl acrylate (IBA) (San Esters Corp., New York,N.Y.).

[0086] DVD Performance Test Method

[0087] An article is placed in a DVD200MG Data Analyzer (DC Associates,Inc., Irvine, Calif.). The software program is activated and the articleis analyzed according to the industry standard entitled, “DVDSpecification for Read Only Disc Pt.1. Physical Specifications, Version1, para. 2.7.3 Random Errors, August 1996,” which provides therequirement for maximum error rate of PI errors for a DVD. A low P1error count generally indicates that the digital transcription processis good and the disc quality is good.

[0088] If the bonded DVD article can be read by the analyzer it isdeemed to have passed the DVD Performance Test.

[0089] Adhesive Preparation

[0090] Syrup Preparation

[0091] 16.5 grams of 2-ethylhexyl acrylate (EHA) (Rohm & Haas,Philadelphia, Pa.) and 8.5 grams of N-vinyl caprolactam (NVC)(International Specialty Products Performance Chemicals, Wayne, N.J.)were combined to form a monomer mixture having a monomer ratio of 66:34EHA/NVC. The monomer mixture was blended with 0.01 grams Irgacure 651photoinitiator. Following dissolution of the photoinitiator, the mixturewas purged with nitrogen gas for about two minutes and then partiallyphotopolymerized with ultraviolet light until the viscosity had risen toa viscosity of at least 200 cps as measured using a BrookfieldViscometer with a No. 4 LTV spindle, at 60 revolutions per minute. Anadditional charge of 0.04 grams of Irgacure 651 photoinitiator was thenadded to the mixture and allowed to dissolve by agitating thecomposition on a roller for about 30 minutes.

[0092] Coating Method A

[0093] The syrup prepared as described above was coated between a T-50silicone-treated, 0.05 mm (2 mil) polyethylene terephthalate (PET)release liner (CPFilms) and a P-10 silicone-treated, 0.05 mm (PET)release liner (CPFilms) using a knife-over-bed coater, and pulling thecoated composite through a coating orifice that was about 50 μm greaterthan the combined thickness of the two release liners.

[0094] Curing Method A

[0095] A coated sample prepared according to Coating Method A was placedunder a ultraviolet light assembly containing four Sylvania blacklightbulbs for a period of 4.5 minutes for a dose of 880 millijoules (NIST)of energy to form an adhesive film about 50 μm thick.

[0096] Curing Method B

[0097] A coated sample prepared according to Coating Method A was passedat a rate of 3 meters/min for a period of about 3 minutes through a UVirradiation chamber that included bulbs having a spectral output of 300nm to 400 nm and a maximum spectral output at 351 nm, mounted above thesample, to form an adhesive film about 50 μm thick. The coated compositewas passed through the chamber with the P-10 release liner as theuppermost layer (i.e., the layer directly exposed to the bulbs). Thetotal measured dosage of energy was 550 milliJoules/cm² (NIST units).

[0098] Coating and Curing Method C

[0099] A PET release liner was unwound from a first unwind roll andpassed over a free-wheeling, unheated steel backup roll 25.4 cm indiameter. A syrup prepared as described above was coated onto therelease liner a coating die similar to that illustrated in FIG. 6 ofVesley et al., WO 95/29811, entitled, “Lamination Process for Coatings.”The die was 91.4 cm wide and was configured with a 0.15 mm brass shim,which was 63.5 cm in length, a 0.254 mm convergence, an overbite of0.076 mm, a coating land L1 of 12.7 mm, a vacuum land of 12.7 mm, and adie attack angle A2 of 90°. Vacuum was applied during the coating. Afterthe coating was applied to the first release liner, a second PET releaseliner was unwound form a second unwind roll and passed around a 2.54 cmdiameter, air pressurized sintered metal laminator bar at an airpressure in the range of 1.4 to 4.5 bar, where it was laminated to thecoated face of the first release liner according to the proceduredescribed in Vesley et al., PCT International Application No. WO95/29766 entitled, “Precision Coating Process for PreparingPolymerizable Films,” to form an uncured laminate construction.

[0100] The uncured laminate construction was cured by passing theconstruction under a bank of fluorescent black light lamps to form anadhesive film of about 50 μm. The laminate construction was exposed toabout 2200 milliwatts/cm² of total energy (NIST units).

EXAMPLE 1

[0101] An adhesive composition was prepared as follows: syrup wasprepared according to the syrup preparation method set forth above withthe exception that the monomers and monomer ratio of the adhesivepolymer was 66/34 isooctyl acrylate (IOA)/N-vinyl caprolactam (NVC). Thesyrup was then coated according to Coating Method A and cured accordingto Curing Method B to form an adhesive film having a thickness of about50 μm.

[0102] Bonded articles to be tested were then prepared as follows usingfirst and second polycarbonate substrates 120 mm in diameter, 0.6 mm inthickness, and having a 15 mm diameter center hole. The adhesive filmwas adhered to the first polycarbonate substrate (designated “C” inTable 1) by passing the adhesive film and the first polycarbonatesubstrate through a bonding nip while applying pressure causing theadhesive film to transfer to the first substrate. The secondpolycarbonate substrate was then adhered to the adhesive film bearingfirst substrate by passing the adhesive film bearing substrate and thesecond polycarbonate substrate through the bonding nip roller such thatthe adhesive coated surface of the first substrate contacted the secondsubstrate forming a bonded article. Two large di-opposed wheels equippedwith vacuum holddown pads were used in the bonding process.

EXAMPLES 2, 3, AND 5-6

[0103] Adhesive films and bonded articles were prepared as describedabove in Example 1 with the exception that the monomers and monomerratio of the adhesive polymers were as follows: 65/35 isooctyl acrylate(IOA)/NVC (Example 2); 64/36 IOA/NVC (Example 3); 65/35 ethylhexylacrylate (EHA)/NVC (Example 5); 64/36 EHA/NVC (Example 6).

EXAMPLES 4 AND 7-14

[0104] Adhesive films and bonded articles were prepared as describedabove in Example 1 with the exception that the monomers and monomerratio of the adhesive polymers were as follows: 60/40 IOA/NVC (Example4); 62/38 isononyl acrylate (INA) (Nikkon Skokubai Co. Ltd., Osaka,Japan)/NVC (Example 7); 61/39 INA/NVC (Example 8); 60/40 INA/NVC(Example 9); 55/45 INA/NVC (Example 10); 62/38 INA/NVP (Example 11);61/39 INA/N-vinyl pyrrolidone (NVP) (International Specialty Products)(Example 12); 60/40 INA/NVP (Example 13); 60/40 IOA/dimethyl acrylamide(DMA) (Jarchem Ind., Newark, N.J.) (Example 14). In addition, thecompositions of Examples 4 and 7-14 were cured according to CuringMethod A instead of Curing Method B.

[0105] The bonded articles of Examples 1-14 were exposed to 90% relativehumidity at 80° C. for 16 hours, according to Accelerated Aging TestMethod I, and then examined for debonding. The results are reported inTable 1.

EXAMPLES 15

[0106] An adhesive film and bonded articles was prepared as describedabove in Example 1, with the exception that there was a layer ofaluminum (designated “A1” in Table 1) on the surface of the secondpolycarbonate substrate and the adhesive composition was in contact withthe layer of aluminum. In addition, the monomers and monomer ratio ofthe adhesive polymer was as follows: 68/32 EHA/NVC.

[0107] The bonded article of Example 15 was exposed to 90% relativehumidity at 80° C. for 16 hours, according to the Accelerated Aging TestMethod I. The article was then examined for debonding, corrosion andpinholes. The results are reported in Table 1.

EXAMPLE 16

[0108] An adhesive film and a bonded article were prepared as describedabove in Example 1, with the exception that the monomers and monomerratio of the adhesive polymers were 55/45 INA/NVC.

[0109] The bonded article of Example 16 was exposed to 90% relativehumidity at 80° C., according to the Accelerated Aging Test Method Iwith the exception that the duration of the test was 1000 hours insteadof 16 hours. The article was then examined for debonding, corrosion andpinholes. The results are reported in Table 1.

EXAMPLES 17 AND 18

[0110] Bonded articles were prepared as described above in Example 1with the exception that there was a layer of aluminum on the surface ofthe first polycarbonate substrate, a layer of silicon dioxide(designated “ST” in Table 1) on a surface of the second polycarbonatesubstrate, and the adhesive composition was in contact with the layersof aluminum and silicon dioxide. In addition, the monomers and monomerratio of the adhesive polymers were as follows: 60/40 INA/NVC (Example17); 65/35 INA/NVC (Example 18).

[0111] The bonded articles of Examples 17 and 18 were exposed to 90%relative humidity at 80° C., according to the Accelerated Aging TestMethod I with the exception that the duration of the test was 1000 hoursinstead of 16 hours. The articles were then examined for debonding,corrosion and pinholes. The results are reported in Table 1.

EXAMPLES 19-22

[0112] Bonded articles were prepared as described above in Example 1with the exception that there was a layer of aluminum on the surface ofthe first polycarbonate disc, a layer of silicon dioxide on a surface ofthe second polycarbonate disc, and the adhesive composition was incontact with the layers of aluminum and silicon dioxide. In addition,the monomers and monomer ratio of the adhesive polymers were as follows:66/34 EHA/NVC (Examples 20 and 21); and 64/34/0.4 EHA/NVC/triethylsilane ((Et₃)SiH) chain transfer agent (Example 22). In addition, Curingand Coating Method C was used instead of Curing Method A and CoatingMethod B.

[0113] The bonded articles of Examples 19-22 were exposed to 90%relative humidity at 80° C. according to the Accelerated Aging TestMethod I with the exception that the duration of the test was 900 hoursinstead of 16 hours. The articles were then examined for debonding,corrosion, and pinholes. The results are reported in Table 1.

EXAMPLES 23-27

[0114] Bonded articles were prepared according to Example 1 with theexception that the first and second substrates both included a surfacelayer of aluminum and the adhesive composition was in contact with thealuminum layers. In addition, the monomers and monomer ratio of theadhesive polymers were as follows: 68/32 IOA/NVC (Example 23); 66/34IOA/NVC (Example 24); 64/36 IOA/NVC (Example 25); 62/38 IOA/NVC (Example26); and 60/40 (Example 27).

[0115] The bonded articles of Examples 23-27 were tested according tothe Cleavage Test Method. The results are set forth in lbs of force toinitiate cleavage in Table 2.

EXAMPLES 28-31

[0116] Bonded articles were prepared according to Example 1 with theexception that the first substrate included a surface layer of aluminumand the second substrate included a surface layer of silicon dioxide.The adhesive composition was in contact with the aluminum surface of thefirst substrate and the silicon dioxide surface of the second substrate.In addition, the monomers and monomer ratio of the adhesive polymerswere as follows: 68/32 EHA/NVC (Example 28); 55/45 IOA/NVC (Example 29);70/30 IOA/NVC (Example 30); 68/32 IOA/NVC (Example 31).

[0117] The bonded articles of Examples 28-31 were tested according tothe Cleavage Test Method. The results are set forth in lbs of force toinitiate cleavage in Table 2.

EXAMPLES 32-38

[0118] Adhesive films were prepared according to Example 1, and weretested according to the Storage Modulus Test Method. Values of G′ at−30° C., 23° C., and 80° C. are set forth in Pascals (Pa) in Table 3A.

[0119] Examples 32-38 were also tested according to the 90° and 180°Peel Adhesion Test Method at 15 minutes and 72 hours. The results areset forth in Oz/in in Table 3B.

EXAMPLES 39-43

[0120] Adhesive films were prepared according to Example 1 with theexception that the following monomers and monomer ratios were used:68/32 IOA/NVC (Example 39); 66/34 IOA/NVC (Example 40); 68/32 EHA/NVC(Example 41); 66/34 EHA/NVC (Example 42); 61/39 INA/NVC (Example 43).

[0121] The adhesive films of Examples 39-43 were then tested for opticalclarity according to the Optical Clarity Test Method. The resultsobtained at 650 nm are reported in % Transmission in Table 4.

Examples 44-47

[0122] Bonded articles were prepared according to Example 1 with theexception that t-butyl acrylamide (t-BAA) was included in the reactionthat produced the adhesive polymer. In addition, the monomers andmonomer ratios were as follows: 60/35/5 EHA/NVC/t-BAA (Example 44);60/35/5 IOA/NVC/t-BAA (Example 45); 60/35/5 INA/NVC/t-BAA (Examples 46and 47).

[0123] The bonded articles in Examples 44-47 were exposed to 90%relative humidity at 80° C. for 16 hours according to Accelerated AgingTest Method I, and then examined for debonding, haze and pinholes. Theresults are reported in Table 5.

EXAMPLES 48-56

[0124] 21.0 grams of IOA and 9.0 grams of N-vinyl caprolactam (NVC)having a monomer ratio of 70/30 (IOA/NVC) were blended with 0.01 gramsIrgacure 651 photoinitiator. The mixture was then purged with nitrogengas for about two minutes and then partially photopolymerized withultraviolet light until the viscosity had risen to at least 200 cps asmeasured using a Brookfield Viscometer. An additional charge of 0.04grams of Irgacure 651 photoinitiator was then added to the mixture andallowed to dissolve by agitating the composition on a roller for about30 minutes.

[0125] The articles were then prepared according to Coating Method A andCuring Method B. The structure of the articles of each example isindicated in Table 6, with where the abbreviations are as follows:C=clear polycarbonate disc, A adhesive, Al=a substrate that includes alayer of aluminum in contact with the adhesive composition, and ST=asubstrate that includes a semitransparent layer in contact with theadhesive composition.

[0126] The samples were then subjected to the Accelerated Aging TestMethod II. The results are reported in Table 6.

EXAMPLES 57-65

[0127] The articles were prepared as described above in Examples 48-56,respectively, with the exception that the adhesive composition includedEHA/NVC in a monomer ratio of 68/32. The structures of the articles ofExamples 57-65 were as indicated in Table 6 and as defined above inExamples 48-56.

[0128] The samples were then subjected to the Accelerated Aging TestMethod II. The results are reported in Table 6.

EXAMPLES 66A AND 66B

[0129] A disc-shaped EHA/NVC 64/34 adhesive film sandwiched between twosilicone treated PET release liners to form an adhesive article, wasprepared according to Example 19. Bonded articles were then preparedusing the EHA/NVC 64/34 adhesive film as follows.

[0130] A disc-shaped polycarbonate substrate suitable for a DVD dischaving a recording capacity of 8 gigabytes, an outer diameter of 120 mm,a thickness of 12 mm and a central hole 15 mm in diameter, was preparedby injection molding polycarbonate into a mold defining a master discaccording to the procedure described in EP 729,141, col. 6, 11. 14-46.The disc-shaped polycarbonate substrate had a first major surface and asecond major surface opposite the first major surface that included pits(i.e., information) created by the injection molding process used toform the disc. An approximately 50 nm thick aluminum layer was sputtercoated onto the structure of pits on the second major surface asdescribed in EP 729,141, col. 6, 11. 47-55.

[0131] The bonded DVD article was prepared using a three chamber vacuumas follows. A semitransparent disc was placed in a first vacuum chamberand centered on a top vacuum plate while vacuum was applied to the firstchamber. The first liner of the disc-shaped adhesive article was removedfrom the adhesive article to expose the adhesive film. The surface ofthe adhesive article that included the second release was then placed ona bottom vacuum plate (release liner side down) in a second chamberwhile applying vacuum. The chambers were then closed via a pneumaticclosing system to form a third vacuum chamber. The third vacuum chamberwas evacuated to about 0.08 millibars of pressure. The lower vacuumchamber was pressurized to about 1 bar causing the bottom vacuum plateto rise such that the adhesive surface of the disc-shaped adhesivearticle contacted the metallized data containing semitransparent surfaceof the polycarbonate disc. The assembly was held in this configurationfor about three seconds, at which time the vacuum to the top plate wasreleased. The second chamber was then evacuated to about 0.08 millibarscausing the lower bonding plate and the bonded assembly now thereon tobe separated from the top vacuum plate. The bonded assembly was thenremoved and placed on the top vacuum plate. The second release liner wasthen removed, exposing the adhesive film. The aluminum surface of asecond polycarbonate disc located on the bottom plate was then broughtin contact with the exposed adhesive film as described above to form thebonded DVD article.

[0132] The bonded DVD article (Example 66A) was then tested according tothe DVD Performance Test Method. The DVD article was capable of beingread by the optical reader and passed the test.

[0133] A second bonded DVD article (Example 66B) was subjected to 100hours of accelerated aging at 85% relative humidity and 80° C. and thentested according to the DVD Performance Test Method. The DVD article wascapable of being read by the optical reader and passed the test.

[0134] Latex Polymerization Method

[0135] 150 grams deionized (DI) water, 0.75 g Rhodacal DS-10 sodiumdodecyl benzene sulfonate surfactant (Rhone-Poulenc), 33 g EHA, and 17 gNVC were charged to a 4-neck flask equipped with a reflux condenser,thermometer, stirrer, and a nitrogen gas inlet. The reaction mixture wasstirred and heated to 60° C. under N₂ atmosphere. When the batchtemperature leveled off at 60° C., the 0.10 g potassium persulfateinitiator was added to the reactor to initiate the polymerization. Afterone hour of reaction at 60° C., the batch temperature was increased to70° C. The reaction was continued at the temperature for two hours tocomplete the polymerization and form a 2EHA/NVC (66/34) latexcomposition. After the reaction, the batch was cooled to roomtemperature and the latex was filtered through a cheesecloth to removecoagulum, if present in the batch. 100 g of the EHA/NVC (66/34)composition, 0.8 Triton GR5M dioctyl sodium sulfosuccinate (UnionCarbide), 1.0 g Polyphobe 101 (Union Carbide) and 0.3 g ammoniumhydroxide were mixed together to increase viscosity and lower thesurface tension of the latex composition.

[0136] The latex polymer was then poured onto a T-50 release linerhaving a 50 μm PET backing coated with a silicone release compound(CPFilms, Martinsville, Va.), and pulled through a knife-over-bedcoating station by hand. The gap between the knife and the bed was setto be 254 μm greater than the thickness of the backing. The coated filmwas air dried at room temperature for about five minutes and then placedin a forced air oven set at 65° C. for 10 minutes. The oven setting wasthen raised to 121° C. and maintained at that temperature for about 10minutes. The temperature was then raised to 149° C. and held attemperature for 20 minutes at which time it was removed from the ovenand allowed to cool to room temperature in the form of a latex adhesivefilm. Upon reaching room temperature the dried latex adhesive film wascovered with P10 release liner having a 50 μm PET backing coated with asilicone release compound (CPFilms).

[0137] Upon unaided eye inspection, the adhesive film was opticallyclear.

EXAMPLE 67

[0138] The above dried latex adhesive film was laminated to a clearpolycarbonate disc and then contacted with a second clear polycarbonatedisc to form a bonded article.

[0139] The bonded article was observed to be optically clear by unaidedeye inspection.

EXAMPLE 68

[0140] A second bonded article was prepared according to the method ofExample 67, with the exception that one of the substrates was a clearpolycarbonate disc and the other substrate was a polycarbonate disc thatincluded an aluminum surface layer.

[0141] The article was visually examined. The bonded article was free ofdebonds and the aluminum surface was reflective.

[0142] Solution Polymerization Method

[0143] 97.84 g of isooctyl acrylate, (IOA) 48.26 g N-vinyl caprolactam,35.75 g isopropyl alcohol, 143.0 g ethyl acetate and 0.2925 g Vazo 67thermal initiator (DuPont) were combined in a 1 liter bottle. Thecontents were then deoxygenated by purging with nitrogen for 2 minutesusing a flow rate of 1 liter per minute. The bottle was sealed andplaced in a rotating water bath at 57° C. for 24 hours to effectpolymerization. The resultant polymer had a measured inherent viscosityof 0.238 dl/g in ethyl acetate at 0.15 g/dl concentration. Per centsolids were measured at 43.07%.

[0144] Coating and Drying of Solution Polymer

[0145] A portion of the above solution polymer was poured onto a 50 μmthick Furon B22 release liner (a PET film coated with a silicone releasecoating, (Furon Company, Worcester, Ma.)) and pulled through aknife-over-bed coating station, by hand. The gap between the knife andbed was set to be 254 μm greater than the thickness of the backing. Thecoated adhesive film was allowed to air dry for 10 minutes and thenplaced in a forced air oven at a temperature of 65° C. The temperaturewas increased to 121° C. over a period of five minutes and then held at121° C. for 20 minutes. The adhesive film was removed from the oven andallowed to cool to room temperature, at which time it was covered with aP-10 release liner (50 μm thick PET film coated with a silicone releasecoating which has a lower level of adhesion toward the dried adhesivefilm vs the Furon B22 release liner). A portion of the adhesive film wasremoved from the release liner and, when inspected by the unaided eye,was found to be optically clear.

[0146] Bonding of Solution Polymer Adhesive Film

[0147] Bonded articles to be tested were then prepared as follows usingfirst and second polycarbonate substrates 120 mm in diameter, 0.6 mm inthickness, and having a 15 mm diameter center hole. The adhesive filmwas adhered to the first polycarbonate substrate by passing the adhesivefilm and the first polycarbonate substrate through a bonding nip whileapplying pressure causing the adhesive film to transfer to the firstsubstrate. The second polycarbonate substrate was then adhered to theadhesive film bearing first substrate by passing the adhesive filmbearing substrate and the second polycarbonate substrate through thebonding nip roller such that the adhesive film coated surface of thefirst substrate contacted the second substrate forming a bonded article.Two large di-opposed wheels equipped with vacuum holddown pads were usedin the bonding process.

[0148] The bonded article was observed by the unaided eye and was foundto be optically clear. TABLE 1 Example Components Formulation ArticleConditions Debonds Corrosion Pinholes 1 IOA/NVC 66/34 C/A/C¹ 80° C. NONENA⁴ NA 2 IOA/NVC 65/35 C/A/C 90% RH NONE NA NA 3 IOA/NVC 64/36 C/A/C 16HOURS NONE NA NA 4 IOA/NVC 60/40 C/A/C NONE NA NA 5 EHA/NVC 65/35 C/A/CNONE NA NA 6 EHA/NVC 64/36 C/A/C NONE NA NA 7 INA/NVC 62/38 C/A/C NONENA NA 8 INA/NVC 61/39 C/A/C NONE NA NA 9 INA/NVC 60/40 C/A/C NONE NA NA10 INA/NVC 55/45 C/A/C NONE NA NA 11 INA/NVP 62/38 C/A/C NONE NA NA 12INA/NVP 61/39 C/A/C NONE NA NA 13 INA/NVP 60/40 C/A/C NONE NA NA 14IOA/DMA 60/40 C/A/C NONE NA NA 15 EHA/NVC 68/32 C/A/Al² NONE NT⁵ NT 16INA/NVC 55/45 C/A/C 80° C. NONE NONE 6 17 INA/NVC 60/40 AL/A/ST³ 90% RHNONE NONE NONE 18 INA/NVC 65/35 Al/A/ST 1000 hrs NONE NONE 2 19 EHA/NVC66/34 Al/A/C 80° C. NONE NONE 5 20 EHA/NVC 66/34 Al/A/ST 90% RH NONENONE 1 21 EHA/NVC 66/34 Al/A/ST 900 hrs NONE NONE 2 22 EHA/NVC/66/34/0.4 Al/A/ST NONE NONE 3 (Et₃)SiH

[0149] TABLE 2 Cleavage (lbs of force Example Components FormulationArticle to initiate cleavage) 23 IOA/NVC 68/32 Al/A/Al 209 24 IOA/NVC66/34 Al/A/Al 240, 260 25 IOA/NVC 64/36 Al/A/Al 254, 300 26 IOA/NVC62/38 Al/A/Al 332 27 IOA/NVC 60/40 Al/A/Al 334 28 EHA/NVC 68/32 Al/A/ST205, 198, 240 29 INA/NVC 55/45 Al/A/ST 282 30 IOA/NVC 70/30 Al/A/ST 30531 IOA/NVC 68/32 Al/A/ST 242, 255

[0150] TABLE 3A G' @ −30° C. G' @ 23° C. G' @ 80° C. Example ComponentsFormulation (Pa) 1*10⁸ (Pa) 1*10⁵ (Pa) 1*10⁴ 32 IOA/NVC 66/34 4.8 14.910.1 33 IOA/NVC 65/35 4.63 15.1 10.8 34 IOA/NVC 64/36 4.27 15.1 9.34 35EHA/NVC 66/34 2.83 6.06 9.36 36 EHA/NVC 65/35 3.33 5.25 9.05 37 EHA/NVC64/36 3.1 5.45 9.29 38 INA/NVC 61/39 3.96 27.2 17.5

[0151] TABLE 3B 90° Peel 180° Peel Adhesion Adhesion (Oz/in) to SS¹(Oz/in) C² C Al/C³ Al/C ST/C⁴ ST/C Example Formulation 15 min 72 hr 15min 72 hr 15 min 72 hr 15 min 72 hr 32 IOA/NVC 61.8 87.2 50.2 63   22  59.8 28   56.7 33 IOA/NVC 62.4 81.4 71.6 94.8 NT⁵ NT NT NT 34 IOA/NVC42.8 77.8 31.2 NT NT NT NT NT 35 EHA/NVC 55.2 72.8 69.9 82   50.4 70.958.1 68.4 36 EHA/NVC 57.6 65.2 NT NT NT NT NT NT 37 EHA/NVC 60.2 75.6 NTNT NT NT NT NT 38 INA/NVC 18.6 33.2 27.8 61.8 25.6 54   23.1 55.6

[0152] TABLE 4 Example Components Formulation % Transmission 39 IOA/NVC68/32 92.85 40 IOA/NVC 66/34 92.72 41 EHA/NVC 68/32 92.81 42 EHA/NVC66/34 92.72 43 INA/NVC 61/39 92.22

[0153] TABLE 5 Ex- For- am- mula- ple Components tion Conditions Result44 EHA/NVC/t-BAA 60/35/5 85° C., 85% RH, no debonding 16 hours or haze45 IOA/NVC/t-BAA 60/35/5 85° C., 85% RH, no debonding 16 hours or haze46 INA/NVC/t-BAA 60/35/5 85° C., 85% RH, no debonding 16 hours or haze47 INA/NVC/t-BAA 60/35/5 85° C., 85% RH, no debonding 16 hours or haze

[0154] TABLE 6 Example Components Formulation Article Debonds CorrosionPinholes 48 IOA/NVC 70/30 C/A/Al NONE NONE 2 49 IOA/NVC 70/30 C/A/AlNONE NONE NONE 50 IOA/NVC 70/30 C/A/Al NONE NONE NONE 51 IOA/NVC 70/30Al/A/Al NONE NONE NONE 52 IOA/NVC 70/30 Al/A/Al NONE NONE NONE 53IOA/NVC 70/30 Al/A/Al NONE NONE NONE 54 IOA/NVC 70/30 Al/A/ST NONE NONENONE 55 IOA/NVC 70/30 Al/A/ST NONE NONE NONE 56 IOA/NVC 70/30 Al/A/STNONE NONE NONE 57 EHA/NVC 68/32 C/A/Al NONE NONE 16  58 EHA/NVC 68/32C/A/Al NONE NONE 2 59 EHA/NVC 68/32 C/A/Al NONE NONE NONE 60 EHA/NVC68/32 Al/A/Al NONE NONE NONE 61 EHA/NVC 68/32 Al/A/Al NONE NONE NONE 62EHA/NVC 68/32 Al/A/Al NONE NONE NONE 63 EHA/NVC 68/32 Al/A/ST NONE NONENONE 64 EHA/NVC 68/32 Al/A/ST NONE NONE NONE 65 EHA/NVC 68/32 Al/A/STNONE NONE NONE

[0155] Other embodiments are within the following claims.

What is claimed is:
 1. An article comprising: a) a first polycarbonatesubstrate; b) a second polycarbonate substrate; and c) an adhesivecomposition disposed between said first polycarbonate substrate and saidsecond polycarbonate substrate such that said first polycarbonatesubstrate is bonded to said second polycarbonate substrate through saidadhesive composition, said adhesive composition comprising an adhesivepolymer comprising the reaction product of 1) an N-vinyl containingmonomer selected from the group consisting of N-vinyl caprolactam,N-vinyl pyrrolidone, and N-vinyl imidazole, and combinations thereof,and 2) an acrylic acid ester monomer of a non-tertiary alcohol having analkyl group comprising 4 to 20 carbon atoms.
 2. The article of claim 1,wherein said article is substantially free of debonding after beingsubjected to Accelerated Aging Test Method II.
 3. The article of claim1, wherein said article is substantially free of debonding afterexposure to 90% relative humidity at 80° C. for 16 hours.
 4. The articleof claim 1, wherein the adhesive composition is substantially free ofbubbles after said article is exposed to 90% relative humidity at 80° C.for 16 hours.
 5. The article of claim 1, further comprising an inorganiclayer disposed on a surface of said first substrate, said adhesivecomposition being in contact with said inorganic layer.
 6. The articleof claim 5, wherein said inorganic layer comprises a metal.
 7. Thearticle of claim 6, wherein said metal layer is reflective to lighthaving a wavelength from 375 nm to 850 nm.
 8. The article of claim 6,wherein said metal is selected from the group consisting of aluminum,silver, brass, gold, gold alloy, copper, copper-zinc alloy,copper-aluminum alloy, aluminum-molybdenum alloy, aluminum-tantalumalloy, aluminum-cobalt alloy, aluminum-chromium alloy, aluminum-titaniumalloy, aluminum-platinum alloy and combinations thereof.
 9. The articleof claim 6, wherein said metal layer is substantially free of corrosionafter said article is subjected to Accelerated Aging Test Method II. 10.The article of claim 6, wherein said metal layer is substantially freeof corrosion after said article is exposed to 90% relative humidity at80° C. for 16 hours.
 11. The article of claim 6, wherein said metallayer is substantially free of corrosion after said article is exposedto 90% relative humidity at 80° C. for 1000 hours.
 12. The article ofclaim 6, wherein said metal layer is substantially free of corrosionafter said article is exposed to 85% relative humidity at 80° C. for 100hours.
 13. The article of claim 5, wherein said inorganic layer issemi-transparent.
 14. The article of claim 5, wherein said inorganiclayer is selected from the group consisting of gold and Si_(n)X_(m),where X is selected from the group consisting of oxygen, nitrogen,carbon, and combinations thereof, and Σ(n+m) satisfies the valencerequirements of Si and X.
 16. The article of claim 1, wherein said firstsubstrate further comprises a metal layer disposed on a surface of saidfirst substrate, and said second substrate further comprises aninorganic layer disposed on a surface of said second polycarbonatesubstrate, said adhesive composition being in contact with said metallayer of said first substrate and said inorganic layer of said secondsubstrate.
 17. The article of claim 16, wherein said inorganic layer issemitransparent.
 18. The article of claim 16, wherein said inorganiclayer is selected from the group consisting of gold and Si_(n)X_(m),where X is selected from the group consisting of oxygen, nitrogen,carbon, and combinations thereof, and Σ(n+m) satisfies the valencerequirements of Si and X.
 19. The article of claim 1, wherein saidarticle is optically clear.
 20. The article of claim 1, wherein saidadhesive composition is optically clear.
 21. The article of claim 1,wherein said article comprises an optical recording medium.
 22. Thearticle of claim 21, wherein said optical recording medium comprisesdata.
 23. The article of claim 21, wherein said optical recording mediumcomprises a storage capacity greater than one gigabyte.
 24. The articleof claim 21, wherein said optical recording medium is selected from thegroup consisting of DVD, DVD-R, DVD-RW, DVD-RAM, DVR, DVD Audio and DVDhybrids.
 25. The article of claim 1, wherein the adhesive polymerconsists of the reaction product of 1) an N-vinyl containing monomerselected from the group consisting of N-vinyl caprolactam, N-vinylpyrrolidone, N-vinylimidazole, and combinations thereof, 2) an acrylicacid ester monomer of a non-tertiary alcohol having an alkyl groupcomprising 4 to 20 carbon atoms, whose homopolymer has a Tg less than 0°C., 3) optionally a monoethylenically unsaturated monomer having from 4to 20 carbon atoms in the alkyl group, whose homopolymer has a Tg ofgreater than 10° C., 4) optionally a substituted acrylamide, 5)optionally an initiator, 6) optionally a cross-linking agent, and 7)optionally a chain transfer agent.
 26. The article of claim 25, whereinsaid article is substantially free of debonding after being subjected toAccelerated Aging Test Method II.
 27. The article of claim 25, whereinsaid article is substantially free of debonding after exposure to 90%relative humidity at 80° C. for 16 hours.
 28. The article of claim 25,wherein said article is substantially free of debonding after exposureto 90% relative humidity at 80° C. for 1000 hours.
 29. The article ofclaim 25, wherein said article is optically clear after exposure to 90%relative humidity at 80° C. for 16 hours.
 30. The article of claim 25,wherein said first substrate further comprises a metal layer disposed ona surface of said first substrate, and said second substrate furthercomprises an inorganic layer disposed on a surface of said secondpolycarbonate substrate, said adhesive composition being in contact withsaid metal layer of said first substrate and said inorganic layer ofsaid second substrate, said article being substantially free ofcorrosion after exposure to 90% relative humidity at 80° C. for 16hours.
 31. An adhesive composition comprising an adhesive polymerconsisting of the reaction product of 1) greater than 30 parts by weightN-vinyl caprolactam; 2) an acrylic acid ester monomer of a non-tertiaryalcohol having an alkyl group comprising 4 to 20 carbon atoms, whosehomopolymer has a Tg less than 0° C.; 3) optionally a monoethylenicallyunsaturated monomer having from 4 to 20 carbon atoms in the alkyl group,whose homopolymer has a Tg of greater than 10° C.; 4) optionally asubstituted acrylamide; 5) optionally an initiator; 6) optionally across-linking agent; and 7) optionally a chain transfer agent.
 32. Thecomposition of claim 31, wherein said adhesive composition is capable ofmaintaining a first polycarbonate substrate in fixed relation to asecond polycarbonate substrate to form an article that is substantiallyfree of debonding after said article is subjected to Accelerated AgingTest Method II.
 33. The composition of claim 31, wherein said adhesivecomposition is capable of bonding a first polycarbonate substrate to asecond polycarbonate substrate to form an article that is substantiallyfree of debonding after exposure to 90% relative humidity at 80° C. for16 hours.
 34. The composition of claim 31, wherein said adhesivecomposition is capable of bonding a first polycarbonate substratecomprising a metal layer disposed on a surface of said polycarbonate, toa second polycarbonate substrate to form an article that issubstantially free of corrosion after exposure to 90% relative humidityat 80° C. for 16 hours.
 35. The composition of claim 31, wherein saidadhesive composition has a storage modulus of at least about 2×10⁵ Pa atroom temperature.
 36. The composition of claim 31, wherein the amount ofsaid N-vinyl caprolactam is from about 33 parts by weight to about 50parts by weight.
 37. The composition of claim 31, wherein said acrylicacid ester monomer is selected from the group consisting of isooctylacrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate,decyl acrylate, lauryl acrylate, hexyl acrylate, butyl acrylate,octadecyl acrylate, and combinations thereof.
 38. The composition ofclaim 31, wherein said adhesive polymer consists of the reaction productof said N-vinyl caprolactam, said acrylic acid ester monomer, and aphotoinitiator.
 39. The composition of claim 31, wherein said adhesivepolymer consists of the reaction product of said N-vinyl caprolactam,said acrylic acid ester monomer, a photoinitiator, and a crosslinkingagent.
 40. The composition of claim 31, wherein said adhesive polymerconsists of the reaction product of said N-vinyl caprolactam, saidacrylic acid ester monomer, a photoinitiator, a crosslinking agent, anda chain transfer agent.
 41. The composition of claim 31, wherein saidadhesive polymer consists of the reaction product of said N-vinylcaprolactam, said acrylic acid ester monomer, t-butyl acrylamide, and aphotoinitiator.
 42. The composition of claim 31, wherein said adhesivecomposition is optically clear.
 43. The composition of claim 31, whereinsaid adhesive composition is optically clear when disposed between afirst polycarbonate substrate and a second polycarbonate substrate andthen exposed to 90% relative humidity at 80° C. for 16 hours.
 44. Anarticle comprising: a first polyethylene terephthalate substratecomprising silicone disposed on a surface thereof; a second polyethyleneterephthalate substrate comprising silicone disposed on a surfacethereof, wherein said first substrate is different from said secondsubstrate; and a pressure sensitive adhesive composition according toclaim 31 disposed between said first substrate and said secondsubstrate.
 45. An article comprising: a) a first polycarbonatesubstrate; b) a second polycarbonate substrate; and c) a pressuresensitive adhesive composition disposed between said first polycarbonatesubstrate and said second polycarbonate substrate such that said firstpolycarbonate substrate is bonded to said second polycarbonate substratethrough said adhesive composition, said article being substantially freeof debonding after exposure to 90% relative humidity at 80° C. for 16hours.
 46. The article of claim 45, wherein said article issubstantially free of debonding after exposure to 90% relative humidityat 80° C. for 1000 hours.
 47. An optical recording medium according toclaim 45, wherein said first polycarbonate substrate comprises data anda metal layer disposed on a surface of said polycarbonate substrate, andsaid data is capable of being read according to the DVD Performance Testafter exposure to 85% relative humidity at 80° C. for 100 hours.
 48. Thearticle of claim 45, wherein said first substrate further comprises ametal layer disposed on a surface of said first substrate, and saidsecond substrate further comprises an inorganic layer disposed on asurface of said second polycarbonate substrate, said adhesivecomposition being in contact with said metal layer of said firstsubstrate and said inorganic layer of said second substrate.
 49. Anarticle comprising: a) a first polycarbonate substrate; b) a secondpolycarbonate substrate; and c) an adhesive composition disposed betweensaid first polycarbonate substrate and said second polycarbonatesubstrate such that said first polycarbonate substrate is bonded to saidsecond polycarbonate substrate through said adhesive composition, saidarticle being substantially free of debonding after exposure to 85%relative humidity at 80° C. for 100 hours.
 50. The article of claim 49,wherein said first substrate further comprises a metal layer disposed ona surface of said first substrate, and said second substrate furthercomprises an inorganic layer disposed on a surface of said secondpolycarbonate substrate, said adhesive composition being in contact withsaid metal layer of said first substrate and said inorganic layer ofsaid second substrate.
 51. An optical recording medium according toclaim 49, wherein said first polycarbonate substrate comprises data anda metal layer disposed on a surface of said polycarbonate substrate, andsaid data is capable of being read according to the DVD Performance Testafter exposure to 85% relative humidity at 80° C. for 100 hours.
 52. Anarticle comprising: a) a first polycarbonate substrate; b) a secondpolycarbonate substrate; and c) an adhesive composition disposed betweensaid first polycarbonate substrate and said second polycarbonatesubstrate such that said first polycarbonate substrate is bonded to saidsecond polycarbonate substrate through said adhesive composition, saidadhesive composition comprising an adhesive polymer consisting of thereaction product of 1) a nitrogen containing monomer that iscopolymerizable with an acrylic acid ester monomer and whose AlogP valueis ≦1.0; 2) an acrylic acid ester monomer of a non-tertiary alcoholhaving an alkyl group comprising 4 to 20 carbon atoms, whose homopolymerhas a Tg less than 0° C.; 3) optionally a monoethylenically unsaturatedmonomer having from 4 to 20 carbon atoms in the alkyl group, whosehomopolymer has a Tg of greater than 10° C.; 4) optionally a substitutedacrylamide; 5) optionally an initiator; 6) optionally a cross-linkingagent; and 7) optionally a chain transfer agent.
 53. The article ofclaim 52, wherein said nitrogen containing monomer has 0.0≦AlogP≦1.0.54. The article of claim 52, wherein said acrylic acid ester monomer hasan AlogP value greater than 1.0.
 55. A method of making thepolycarbonate article of claim 1, said method comprising: 1) contactingsaid first polycarbonate substrate with said adhesive composition; and2) contacting said adhesive composition with said second polycarbonatesubstrate such that said first polycarbonate substrate becomes bonded tosaid second polycarbonate substrate through said adhesive composition.